GRAHAM WARWICK / WASHINGTON DC
Liquid crystal displays set to replace cathode-ray tubes as technology advances
Suppliers expect liquid-crystal displays (LCD) will begin replacing cathode-ray tubes (CRT) in head-up displays (HUD) within the next two to three years, as key technical issues are overcome.
Thales Avionics is demonstrating an LCD HUD and FedEx Express has selected a Honeywell LCD HUD to be installed on its widebody fleet from 2007 as part of an enhanced vision system (EVS) (Flight International, 14-20 October).
CRTs are becoming difficult to source because of obsolescence, says Kevin Young, Honeywell director, air transport display systems, adding: "The mean time between failures [MTBF] for CRTs is fairly low, because the phosphor wears out." But the main driver behind the move to LCDs is the development of EVS and the resulting need for higher image quality.
In an EVS HUD, a CRT has to steer the same electron beam to generate the infrared image by raster-scanning like a television then superimpose flight symbology by stroke-writing like an oscilloscope. This limits resolution and brightness. An LCD has fewer limitations, and can generate symbology and imagery simultaneously with a higher contrast ratio. "An LCD's capability is driven by computing power," says Young.
Flat-panel LCDs are also more compact, lighter and more reliable than CRTs. "MTBFs are four to five times those of CRTs," says Young. LCDs began replacing CRTs in head-down displays some years ago, but HUDs posed a greater challenge. "The problem with using LCDs in HUDs is getting enough light through them. That issue has been solved," he says. The HUD market is also expanding, and displays will soon be available on most business and commercial aircraft.
Under FedEx's Magic Window programme, Honeywell's LCD HUD will be certificated on the Boeing MD-10 in 2006, followed by the MD-11 and Airbus A300 and A310, with fleet installation beginning in 2007.
Working with Airbus, Thales plans to have an LCD HUD available for flight testing by the end of next year, and expects certification less than a year from then. The French manufacturer says US low-cost carrier JetBlue is looking at LCD HUDs for its A320s.
Source: Flight International
